Safety switch



Nov. 21, 1950 N 2,530,461

SAFETY SWITCH Filed Aug. 51, 1948 2 Sheets-Sheet 1 INVENTOR. R.A.'GUNDMJM A TTORNE YS Nov. 21, 1950 sum: 2,530,461

SAFETY SWITCH Filed Aug. 31, 1948 2 Sheets-Sheet 2 F/G. 3 F/G. 4

8 SAFETY g wncH" F/GB SAFETY VF SWiTCH SAFETY INVENTOR. SWITCH RVA.GUND

BYMIM A TTORNEYS Patented Nov. 21, 1950 UNITED STATES "PATENT OFFICESAFETY SWITCH Russell A. Gund, Tulsa, Okla, assignor to PhillipsPetroleum Company, a corporation of Delaware Application August 31,1948, Serial No. 46,997

5 Claims. i

This invention relates to a safety switch. In one specific aspect itrelates to a safety switch for a walking beam. Another aspect of theinvention is that it relates to switches actuated by acceleration of theswitch housing of a predetermined magnitude and operating by inertia ofpart of the switch.

There are numerous applications where it is desirable to have a safetyswitch mounted on a moving piece of machinery so that machinery may bestopped in case it runs wild.

In the art of pumping oil wells by means of a pump at the bottom of thewell actuated by a string of sucker rods, the sucker rods being moved upand down by a walking beam, it is very important to stop the actuationof the walking beam when anything goes wrong, especially if the stringof sucker rods breaks. In many instances, the well is located at aremote point and is only visited by an operator once a day. Therefore,if anything goes wrong a considerable amount of destruction can occurbefore the return of the operator. Also as the pumping device is inbalance when a long string of sucker rods and a heavy column of oilbeing pumped is supported, obviously the device will be entirely offbalance when the rod string breaks and no oil is being pumped. Thewalking beam unit will tear itself to pieces under such conditions ifallowed to continue to run.

One object of the present invention, therefore, is to provide a systemincluding a switch for stopping the walking beam when the rod linebreaks.

Another object is to provide a rugged, simple, and eflicient switch forsuchan installation.

Further object is to provide such a switch which may be readily attachedto a portion of the walking, beam or other similar reciprocating oroscillatin element of a machine.

Another object is to provide a switch which is actuated by apredetermined acceleration of its housing and which may be reset by theoperator in a single operation.

Numerous otherobjects and advantages will be apparent to those skilledin the art upon reading the accompanying specification, claims anddrawings.

In the drawings Figure 1 is an elevational view of a walking beam oilwell pump embodying the present invention.

Figure 2 is an elevational view with the cover removed of a switchembodying the present invention and adapted to be used in the structureshown in Figure 1 and in similar situations.

Figure 3 is a cross-sectional view of a fragmentary portion of Figure 2showing detail of construction.

Figure 4 is an elevational view of a portion of Figure 2 showing how themercury switch may be reversed in its position so as to furnish a contact-breaking switch instead of a contact-making switch.

Figure 5 is a wiring diagram showing how the primary or secondary of amagneto ignition system may be grounded by a safety switch of the typeshown in Figure 2.

Figure 6 is a wiring diagram similar to Figure 5 showing how a batteryignition system may be grounded by the switch of Figure 2.

Figure 7 is a wiring diagram showing how the safety switch of Figure 2may be employed to actuate a circuit breaker when the prime mover of thewalking beam is an electric motor.

Figure 8 is a wiring diagram showing how the safety switch of Figure 4may be employed to directly interrupt the source of electric power whenthe prime mover of the Walking beam is an electric motor.

In Figure 1 an oil well I l is being pumped by a pump (not shown) in thebottom of the well actuated by a string of sucker rods l2. The suckerrods 12 are moved up and down by a walking beam 13 pivoted on asupporting structure It and actuated by a pitman l5 driven by a crank l1operated by gears in gear box 18 driven by internal combustion engineI9.

As such internal combustion engine driven walking beam pumping units areold, no description of the component parts will be made, except to statethat during normal operation the sucker rod l2 and the column of oil inwell ll being moved by sucker rod I2 into flow line 2| has considerableweight and this Weight is balanced on pivot [4 by a counterweight 22.

The internal combustion engine H] has an ignition system and anelectrical circuit comprising wires 23 and 24, and a switch (shown inFigure 2) completes this circuit inside housing 26.

The details of the preferred form of the switch inside of housing 26 areshown in Figure 2.

The housing 28 may be provided with a cover (not shown) which may besecured by any suitable means such as screws in holes 21. Housing 26 isalso preferably provided with a bifurcated portion comprising lugs 28and 29 which are adapted to engage a portion or" the walking beam orother reciprocating or oscillating member by means of a set screw 31which may be provided with a lock nut 32. As will be apparent in Figure3 1, the walking beam i3 is generally provided with some element such asflange 33 which may be engaged by the bifurcated portions 28 and 29.Wires 23 and 24 of Figure l are integral with, or are connected to,wires 13 and 14 respectively of Figure 2.

A combined weight, switch actuating, and reset member 34 is pivoted tothe housing by and rotates around the axis of screw 35.

As shown in Figure 3 screw 36 may be provided with an anti-frictionsleeve 3'! and a washer 38 for preventing displacement of member 34.Housing 23 may also be provided with a boss, or raised portion, 39,spacing member 34 out of frictional engagement with the wall of housing26. The construction of Figure 3 is preferable in that better or moreuniform results are obtained especially in instances where the switchhas not operated over a long period of time. One of these switches whenmounted on a walking beam might not be called on to operate for as muchas a year, but when the time to operate comes it is very important thatsatisfactory operation occurs as otherwise valuable machinery, andperhaps even a valuable oil well, may be completely ruined.

Member, or arm, 34 comprises a Weighted portion as obviously thatportion of arm 34 which lies to the right of the aXis of screw 36 ismuch heavier than that portion lying to the left of said axis. Arm 34has a notch 4| formed in the free end thereof and is preferably alsoformed with a bevel 42. The functions of notch 4| and bevel 42 will bediscussed below under the operation of the device, but it will be notedthat notch M is receiving the end 43 of a latch member 44. Furtherupward movement of any substantial nature by the notch end of arm 34 isprevented by an outstanding pin or boss 46 which is mounted on or is anintegral part of housing 26.

Latch 44 is pivoted for rotation around the axis of screw 41. Screw 41is preferably constructed in the same manner as screw 36 as shown inFigure 3, washer 48 corresponds to washer 38, boss 49 corresponds toboss 39, and preferably an antifriction sleeve (not shown) correspondingto sleeve 31 is also provided. The corresponding parts have the samefunctions.

Latch 44 is provided with a suitable spring engaging means shown in thedrawing as a boss formed integral with latch 44. Latch 44 in a positionshown in Figure 2 is being urged into engagement with notch 4! by abiasin means preferably comprising a helical compression spring 52. Theother end of spring 52 is mounted on an adjustable spring mounting 53preferably formed in the end of a set screw 54. Set screw 54 is threadedthrough housing 26 and engages threads 56 in said housing so that byrotating set screw 54 spring support 53 may be moved to the right orleft thereby varying the compressive force of spring 52 as will beexplained when discussing the operation of the device. A look nut 51 ispreferably provided to fasten set screw 54 in adjusted position. Whenlatch 44 is not engaging notch 4| any substantial counterclockwiserotation of latch 44 is prevented by pin or boss 58 secured to or formedin housing 26 in a manner similar to pin or boss 46.

The portion of arm as to the left of pivot 36 is the reset portion ofthe arm and is provided with a means for moving arm 34 back into theposition shown in Figure 2. This means cooperating with said resetportion for moving said member 34 into engagement with said stop 46preferably comprises a hole 59 receiving lanyard or reset pull cord 6!.Cord 6| may be provided with any simple knot or other engaging means 62and noted to indicate the position of cord GI and thereby the positionof arm 34. Cord 6| may be provided with a position indicating marker 63preferably consisting of a split lead sleeve clamped around the cord.However, a painted mark on the cord or other means may be employed.Marker 63 is positioned so that when arm 34 is in its tilted position(not shown) marker 63 will be near housing 26. Cord 6| may pass througha hole 84 in housin 26.

On arm 34 there is mounted by any suitable means, such as spring clip66, a gravity actuated switch 81. Switch 61 may be any gravity actuatedswitch but it is preferable to use a mercury switch of the type shownespecially when operated near oil well I I as the glass envelope 68prevents sparks from contacts 69 and H from accidentally starting a firein case the mercury 12 should produce an arc.

As shown in Figure 4, it is very easy to reverse the position of switch61 in spring clip 66 so that tilting the arm 34 will open the circuitinstead of closing the same.

In Figure 2 switch 61 is preferably connected to wires 13 and 14 incable 16 by wires 71 and 18.

connected respectively to contacts 69 and H. Wires 1'! and 18 havesuflicient slack so that pivoting of arm 34 around pivot 36 is notimpeded unduly. Wire 13 is connected to wire 18 and wire 14 is connectedto wire 11 but any suitable means preferably a wire positioning andconnecting junction board 19 secured by screws to housing 26 may beused. A cleat or clamp 81 may be provided to hold the end of cable 16against housing 26 and the inner edge of hole 82 in housing 26 may belined with a. rubber grommet 83 to prevent wear on the cable.

Figure 5 is a wiring diagram showing the use of primary 84 or thesecondary 86 of a magneto ignition system for an internal combustionengine [9 which may be grounded by a safety switch 26 of the type shownin Figure 2 depending upon the position of switch 81. With switch 81 inthe position shown primary 84 is grounded but if switch 81 contacts 88then secondary 86 will be grounded. Part 89 is the magneto, 9| thecommutator, 92 one of the spark plugs, and 93 the breaker contactmechanism. As such magneto ignition systems are known, no furtherdescription of the same is made.

Figure 6 is a wiring diagram similar to Figure 5 showing a batteryignition system powered by battery 94. The safety switch 28 is shown asa means for grounding primary circuit 96 but obviously it could be usedto ground secondary circuit 91. Also by inverting the position of switch61 from that shown in Figure 2' to that shown in Figure 4 and connectingsafety switch 26 in series in wire 96 instead of grounding the same at98 the safety switch can be used to interrupt the primary circuit andcould be so used in Figure 5 in primary circuit 84. Also it could beused to interrupt secondary circuit 31 in Figure 6.

Figure 7 is a wiring diagram showing how the safety switch 26 may beemployed with a battery 99 and a solenoid IOI to operate a circuitbreaker I02 by means of an armature Hi3. Circuit breaker Hi2 interruptsthe power circuit I04 of electric motor 106. Electric motor I06 isreplacing the internal combustion engine 19 of Figure 1.

While electric motor controls shown in Figure '7 is preferred, it ispossible to employ safety switch 2'5 directly in power line l! of motorI08. In Figure 7 safety switch 26 has a normally open switch bl in theposition shown in Figure 2 whereas in Figure 8 safety switch 26 is ofthe normally closed type shown in Figure 4.

Operation In Figure 1 during normal operation internal combustion engineit is running driving the gears in portion ES and rotating crank I!which oscillates walking beam 43 about pivot l4 by means of pitman 56.Rod line 12 slowly rises and falls in well H actuating the pump (notshown) to pump a column of oil from i l into pipe 2|. The weight of rodsl2 and the oil is in part counterbalanced by counterweight 22. Becauseof the load on motor Iii the movement is somewhat deliberate and theacceleration of housing 26 mounted on flange 33 of walking beam [3 doesnot exceed a predetermined amount.

Motor it is preferably Wired up as shown in Figure 5 and preferablymagneto 89 is adapted to be grounded through the primary circuit 84 andsafety switch 26 when arm 3 in Figure 2 rotates clockwise until mercury'12 contacts both contacts 69 and H Rod 12 is subject to considerablestrain and stress and sometimes breaks. This reduces the load on engine!9 and also counterweight 22 is no longer counterbalanced. As a resultswitch housing 2b is accelerated more than the predetermined amountnecessary to actuate arm 34.

As shown in Figure 2 a sudden upward acceleration of housing 26 developssufficient inertia in the right hand portion of arm 34 to cause the armto rotate around pivot 36 in a clockwise direction and forces the end 43of latch 44 out of notch 4|. The amount of acceleration necessary to dothis can be predetermined by adjusting the compression of spring 52 byset screw 54. When arm 34 has rotated until 43 is clear of notch 4| theforce of gravity will then pull arm 34 down and move mercury 12 intocontact with contacts 69 and H thereby closing switch 61 and connectingwires 13 and 14.

This movement pulls lanyard 6| in through hole 64 so that indicator 63is adjacent housing 26. Counter-clockwise movement of latch 44 islimited by pin 58.

To reset the switch lanyard 61 is pulled and beveled surface 62 pushesend 43 into notch 4| while pin 45 prevents movement of 34 further thannecessary, prevents end 43 from going below notch 4i. The switch is thenreset and will operate automatically on the next acceleration greaterthan a predetermined magnitude.

The operation of the switch shown in Figure 4 is the same as that shownin Figure 2 except that actuation of the switch breaks a contact insteadof making a contact between contacts 69 and 'H.

The operation of Figures 5, 6, '7 and 8 are believed obvious. Uponactuation of the safety switch 26 by excessive acceleration, magneto 89in Figure 5 is grounded and internal combustion engine i9 stops due tofailure of the ignition system. The same action takes place in Figure 6.In Figure 7 the closing of the circuit of safety switch 25 as in Figure2 opens the power circuit I04 of motor I66. Similarly in Figure 8 theactuation of safety switch 25 as in Figure 4 interrupts power circuitI01 of motor I08.

In the specification the preferred form and embodiment of the inventionhas been shown for the purposes of illustration and the scope of theinvention is not limited thereby but is defined in the following claims.

Having described my invention, I claim:

1. A safety switch adapted to be carried by a walking beam comprising,in combination, a housing, a combined weight, switch actuating and resetmember pivotally mounted on said housing, said member including aweighted portion at one side of said pivot having a notch formed in thefree end thereof and a reset portion at'the other side of said pivot, astop limiting the pivotal movement of said member, means cooperatingwith said reset portion for moving said member into engagement with saidstop, a latch biased into engagement with the notch in said weightportion for normally holding said member adjacent said stop, said memberbeing disengageable from said latch upon acceleration of said housing ofa predetermined magnitude due to the inertia of said weighted portion,and a switch carried by said member, the switch being actuated when theweight portion is displaced from said stop upon said predeterminedacceleration.

2. A switch comprising, in combination, a housing, a unitar weight,switch actuating and reset member pivotally mounted on said housing,said member including a weighted portion at one side of said pivothaving a notch formed in the free end thereof and a reset portion at theother side of said pivot, a stop limiting the pivotal movement of saidmember, a pull cord secured to said reset portion for rotating saidmember into engagement with said stop, a latch pivotally mounted on saidhousing, a spring biasing said latch into engagement with the notch insaid weight portion for normally holding said member adjacent said stop,said member being disengageable from said latch upon acceleration ofsaid housing of a predetermined magnitude due to the inertia of saidweighted portion, and a switch carried by said member, the switch beingactuated when the weight portion is displaced from said stop upon saidpredetermined acceleration.

3. A switch comprising, in combination, a housing, a unitary weight,switch actuating and reset member pivotally mounted on said housing,said member including a weighted portion at one side 01' said pivot anda reset portion at the other side of said pivot, the free end of one ofsaid portions having a notch formed therein, a stop limiting the pivotalmovement of said member, a. pull cord secured to said reset portion forrotating said member into engagement with said stop, a latch pivotallymounted on said housing, a spring biasing said latch into engagementwith the notch in said weight portion 101' normally holding said memberadjacent said stop, said member being disengageable from said latch uponacceleration of said housing of a predetermined magnitude due to theinertia of said weighted portion, and a switch carried by said member,the switch being actuated. when the weight portion is displaced fromsaid stop upon said predetermined acceleration.

4. A switch comprising, in combination, a housing, a unitary weight,switch actuating and reset member pivotally mounted on said housing,said member including a weighted portion at one side of said pivothaving a notch formed in the free end thereof and a reset portion at theother side of said pivot, a stop limiting the pivotal movement of saidmember, means cooperating with said reset portion for moving said memberinto engagement with said stop, a latch biased into engagement with thenotch in said weight portion for normally holding said member adjacentsaid stop, said member being disengageable from said latch uponacceleration of said housing of a predetermined magnitude due to theinertia of said weighted portion, and a switch carried by said member,the switch being actuated when the weight portion is displaced from saidstop upon said predetermined acceleration.

5. A switch comprising, in combination, a housing, a unitary weight,switch actuating and reset member pivotally mounted on said housing,said member including a weighted portion at one side of said pivot and areset portion at the other side of said pivot, the free end of one ofsaid portions having a notch formed therein, a stop limiting the pivotalmovement of said member, means cooperating with said reset portion formoving said member into engagement with said stop, a latch carried bysaid member, the switch being actuated when the weight portion isdisplaced from said stop upon said predetermined acceleration.

RUSSELL A. GUND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,902,371 Miller et al Mar. 21,1933 2,280,114 Athy Apr. 21, 1942 20 2,360,561 Holderson Oct. 17, 19442,436,518 Lieifers et a1 Feb. 24, 1948

